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Post by coherentsheaf on Jun 20, 2014 14:57:45 GMT 5
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Post by creature386 on Jun 20, 2014 16:49:12 GMT 5
Paywalled, damn it. But at least I know can be more sure about it when citing McHenry.
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Post by Godzillasaurus on Jun 21, 2014 1:43:35 GMT 5
I kind of figured that they wouldn't have a high capacity to use torsion and heavy twisting to feed; their jaws were notoriously shallow and not necessarily particularly broadened (at least to the point where they would be considered super wide structures. The snout tips were awfully slender, but yet their jaws were more robust in the posterior regions at the same time) What does it imply by " post-symphyseal"  |
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Post by creature386 on Jun 21, 2014 1:58:26 GMT 5
A symphysis is a part of the lower jaw (look it up) and post-symphyseal simply means behind it. To take Liopleurodon as an example, the post-symphyseal part starts after the 6th or 7th alveolar when going from the rostral to the caudal part or the jaw.
In simple terms, it is the posterior part of the jaw.
P.S. Now I finally know why Liopleurodon and even some Pliosaurus species evolved a short symphysis.
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Post by Godzillasaurus on Jun 21, 2014 2:02:23 GMT 5
I looked it up but couldn't find anything. I don't know why a killing style where the posterior parts of the jaws are used; that area is extremely inefficient at killing unless the said prey item was being crushed (not to mention very small). The largest teeth are present in the frontal half of the jaws, and that is where the biggest gape would be located (albeit not the most powerful region in terms of bite force), so that killing style does not seem ideal
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Post by theropod on Jun 21, 2014 2:39:24 GMT 5
The largest teeth in the upper jaw are actually post symphyseal in both Pliosaurus and Kronosaurus. Pliosaurs would have relied on crushing to a great deal, that is what their enourmous adductor chambers and robust (either triangular or round crosssection), deeply rooted teeth suggest. Don’t forget in crocodilians we also find the most robust skulls less linked to bite force than to resistance to struggling prey and postcranial forces. Logically, the anterior dentition would have made initial prey contact, but the bulk of the damage done and the force excerted would have then been transmitted by the intermediate or posterior dentitions, since those are the parts of the mouth with the best mechanical advantage and the longest teeth respectively. There’s nothing strange about that, crocodiles trying to crush a turtle also don’t do so with their caniniform teeth. The results are deceiving, since they where compared at equal snout lenghts. Pliosaurs have way longer skulls than the majority of other predators at equal body size, so if skull size was corrected for we have to keep in mind the skull would be larger overall, with its relatively greater size correcting for its weaker construction. Also, P. kevani’s bending resistance in the plot seems broadly similar to C. niloticus. The bite force estimate was also similar to one derived for a crocodile of the same skull lenght using multibody-dynamics-simulations, however in-vivo bite forces where way higher (and the same may also be true for pliosaurs). Research on the relevant terminology should have turned up this→, I remember searching for the same thing a few years ago while reading a description of Simolestes. The post-symphyseal part is everything behind the symphysis. btw this confirms what I once theorized, pliosaurs probably relied on prey smaller than themselves (at least in most cases). |
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Post by Godzillasaurus on Jun 21, 2014 3:42:22 GMT 5
Wait, I'm confused... Creature said that a symphyseal is the posteriormost region of the jaw while online it states that it is the tip region of the mandible. If the latter is true, then of course the longest teeth would be post-symphyseal (the longest are NOT located in the rearmost region of the jaw. This is common for most predatory animals that do not hunt shelled creatures, because it would be completely inefficient as opposed to if they were longest in the front half).
Most definitely, but not in the same sense as what we would expect to see from something that hunts shellfish (example, Chinese alligator): in which case we would expect its teeth (despite still being very thick and robust, albeit still pointed) to have been much shorter and blunter while having a much proportionally broader jaw shape. It seems as if they would have hunted similar to tyrannosaurids: by inflicting major piercing wounds through the combination of their powerful bites and thickened, spike-like dentition
Except that the paper explicitly stated that pliosaurs were highly adapted (and probably did, most of all) for attacking largish marine reptiles and fish: "we conclude that Late Jurassic pliosaurs were generalist predators at the top of the food chain, able to prey on reptiles and fishes up to half their own length."
Most likely, but yet their morphology still seems to imply that their diet was made up primarily of itchthyosaurs and smaller plesiosaurs (and fish in smaller individuals/species) as opposed to hard-shelled prey like turtles. Pliosaurs were most definitely apex macropredators during the Late Jurassic in oceans (and the Early Cretaceous for kronosaurus)
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blaze
Paleo-artist 
Posts: 766
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Post by blaze on Jun 21, 2014 9:00:01 GMT 5
He said that post-symphyseal meant the posterior part of the jaw (posteriormost and simply posterior are not the same thing). btw check one of the authors of that paper, Michael J. Benton, remember that I shared in another thread the link to where he posts reprints of his papers? this paper is there ( link). |
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Post by creature386 on Jun 21, 2014 13:05:11 GMT 5
Yeah, a symphysis in pliosaurs is if anything actually located more anteriorly because, as I said, Liopleurodon and some others only have like 7 teeth in front of it. The pre-symphyseal part may be seen as the premaxilla of the mandible. Here what it is: "the symphyses between the bones of the skull, a common misperception about the mandible is that the (symphysis menti) (chin) is a symphyseal joint. This is a misnomer as the two halves of the mandible formed from the mandibular arch mesoderm are fused early in life and ossify to form one single bone" en.wikipedia.org/wiki/SymphysisP.S. Thx for the paper blaze! |
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Post by theropod on Jun 21, 2014 15:17:16 GMT 5
Probably yes. What’s your point? I don’t know how that disagrees with what I wrote. I think in general pliosaurs would have relied much less on gripping and seizing than crocodilians. Their huge skulls and different teeth allow for different strategies. Smaller prey relative to themselves, not small prey. We are still talking about animals that I’ll wager could have attacked pretty much everything during their day. Most of their potential prey would have been smaller than themselves simply due to ecological sampling. A less demanding alternative to shake and twist feeding is represented by preferential biting at the large post-symphyseal teeth, as observed in many modern croc- odilians. After capture, prey could be repositioned with a series of inertial bites and then killed by powerful crush-
ing bites, in line with the large median teeth. This cycle is repeated until the prey item is killed and the mechanical resistance of prey is weakened (Cleuren & De Vree, 2000). I fully agree with the authors. |
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Post by creature386 on Jun 21, 2014 15:54:38 GMT 5
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Post by Infinity Blade on Jun 21, 2014 16:09:25 GMT 5
I was always under the impression these pliosaurs had vastly superior bite forces to T.rex. Then I looked into here and one paper with Kronosaurus, and I guess I may be wrong for at least these two guys.
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Post by coherentsheaf on Jun 21, 2014 16:16:02 GMT 5
I was always under the impression these pliosaurs had vastly superior bite forces to T.rex. Then I looked into here and one paper with Kronosaurus, and I guess I may be wrong for at least these two guys. No in the context of the same study, a 6 tonne Kronosaurus had a siilar bite force to Sue (FMNHPR 2081), which probably weighed soewhere between 8 and 9 tonnes. I think we have reasonable evidence that Pliosaurs had similar bite forces to Tyrannosaurus. |
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Post by Grey on Jun 22, 2014 4:31:39 GMT 5
Well, theoretically, which pliosaur has the most powerful bite and which one has the most resistant skull structure ? Pliosaurus kevani or Kronosaurus ?
Somehow I'm not surprised of these very powerful bite forces but I'm not surprised either that they do not yield results in the 150-200 kN like some suggested earlier (P.X hype).
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Post by Infinity Blade on Jun 22, 2014 4:38:50 GMT 5
I was always under the impression these pliosaurs had vastly superior bite forces to T.rex. Then I looked into here and one paper with Kronosaurus, and I guess I may be wrong for at least these two guys. No in the context of the same study, a 6 tonne Kronosaurus had a siilar bite force to Sue (FMNHPR 2081), which probably weighed soewhere between 8 and 9 tonnes. I think we have reasonable evidence that Pliosaurs had similar bite forces to Tyrannosaurus. You mean this study (hyperlink)? |
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